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NHRA - National Hot Rod Association

Peak Did You Know? What happens when a nitro engine scuffs a piston

An inside look at the thermal damage that leads to dramatic smoke shows on the dragstrip
07 Oct 2024
Posted by NHRA.com staff
Feature

In a recent Peak Did You Know segment on the NHRA on FOX broadcast, Tony Pedregon explained the intense mechanics of what happens when a Top Fuel or Nitro Funny Car engine scuffs a piston.

A lean fuel mixture creates excessive heat, which thermally destroys one or more of the engine’s pistons. As the piston deteriorates, oil from the crankcase leaks past it and enters the combustion chamber. This oil, now mixed with nitro fuel, is then pumped out of the exhaust and produces a dramatic smoke show that can rival the car's burnout.

Pedregon uses a detailed animation to illustrate how this excessive heat not only damages the pistons but also leads to a visual spectacle that fans recognize as more than just a typical engine failure — it’s the result of the raw power and complexity of these high-performance machines.